Impossible
by Thegirlwiththekey
Summary: Sherlock and John defy Lestrade and visit a disused building no-one else will. A decision, they soon regret.
1. Chapter 1

They both ran, hearts pounding through the dark. Sherlock, the taller of the pair was taking much larger strides and John was falling behind. He could still hear his voice rasping behind him so he knew he was still somewhere behind. He called out.

"John!"

"I'm...here" he shouted back.

The air was dusty and dank. It was cold and Sherlock's breath swirled around him. He thought he might be sick but kept running. He pumped his arms and legs faster, willing an escape to appear. No-one else knew they were here. If they had to get out they had to do it themselves. He darted in between pillars and unidentified objects. He could barely see as his torch flicked light around wildly as his arms swung backwards and forwards.

Sherlock saw a light up ahead. Not from his torch, this light held steady. It was glowing through the gap in between a door and its frame. Relief warmed through him. He launched himself through the dark into the wood. It splintered and the door swung open and blinding sunshine momentarily dazzled him. He put his hand against a moss covered wall and bent double gasping for breath. John tumbled out of the darkness behind and leant against the wall. They looked at each other. John saw something in Sherlock's eyes he hadn't before.

Fear.

Finally John had caught his breath enough to speak.

"What, was that?!" He exclaimed. Sherlock's face told him he didn't know either. Looking back into the dark building they had fled from Sherlock shook his head from side to side slowly.

"It's just not possible" he muttered to himself. "It can't be."

Slowly they both walked away from the building rounding a corner. London reappeared. People bustled past, unaware of the danger to them just a few buildings away.

"I take it we aren't going to tell Lestrade about this" Whispered John, now alert to anyone around them. Again, Sherlock's face said enough.

No.


	2. Chapter 2

Back inside 221b John went to his room and sat on the edge of his bed. He ran his hands though his hair, got up and went to look out of his window. Nothing seemed different. He sat back on the bed and asked himself what he had expected to see. He couldn't answer, so he took off his shoes, placing them next to his bed, lined next to each other and facing out. Habits from the army he couldn't break. Standing up, he smoothed out the creases from where he had sat and walked into the living room.

Sherlock was lying on the floor face upwards, hands clasped together on his stomach. Apart from his odd choice of place to lie he looked peaceful. His eyes snapped open when John shuffled in. Still lying on the floor he looked John toe to head but said nothing. John sat on the sofa and sighed.

"Why are you on the floor?" he asked in a way that suggested the question pained him slightly to say it. Sherlock tilted his head towards john.

"Storing and remembering" he answered nonchalantly.

"On the _floor?"_

"The brain stores and recalls information better in strange environments. So by lying down here I can store more detail than usual."

John didn't think two of those things could be possible; the first being that Sherlock could store more information than normal. The second being that a possible detail from today's events could ever be forgotten.

"Sherlock, you're the most rational man I know-"

"Thank you" Sherlock responded before John had finished his sentence.

"I'm not sure it's a compliment Sherlock. Sometimes you put rationality before other people's feelings". He trailed off. Sherlock had closed his eyes again and cocked his shoulder slightly to show he wasn't listening anymore and didn't care either. John began to speak again and Sherlock snapped his eyes open, rolling them dramatically.

"Anyway, you saw the same as me. But it's just not possible. I know Lestrade told us not to go there but I never thought..."

Sherlock sat up, leaning on his hands that he placed behind him.

"Listen to me John. We have both been duped. What that was, back there. Not possible. Illogical, inconceivable and absurd. Just forget about it."

"But back at the building you believed it too. I heard you say 'it can't be'. That means you believed it too doesn't it?" John asked anxiously.

"No John. I have thought it all through and there are many different explanations for what we saw."

John was losing his temper now.

"SHERLOCK. I SAW IT, YOU SAW IT! It was a... zombie." He said the last word quietly as if one could walk in at any moment.

Sherlock snorted at the ridiculous word.

"John, the undead are not roaming the streets of London, or shuffling around a deserted building for that matter. Don't use that word either. You sound like Anderson."

Anger and fear bubbled inside John, closing his eyes he began to relive the day's events...


	3. Chapter 3

Sherlock was darting around the back of the building looking for a door or a "hidden entrance". John stood back with his arms folded disapprovingly.

"So let me get this straight. You hacked Lestrade's computer, traced the mobile phone signal of the missing man, which stopped here. He found out, got cross and banned you from the case?"

"Essentially, yes." Sherlock mused, examining each brick in turn. "But look, he hasn't even bothered to follow up my lead. Not a single officer here. If their phone is here then they might be too."

"But there must be a reason Lestrade told you not to go into this building."

"Yeah, it's an ex-diplomat's building. Technically he still owns it. But look he hasn't exactly looked after it well has he!"

"So solving this case and finding the missing man means less Lestrade than some diplomat's manky building?"

"Not Lestrade's decision. Way above his head that decision. This particular diplomat could make things very difficult for Britain if he so chooses. I however, have no care for such trivialities."

He suddenly gripped a drainpipe that was fixed to the wall and rattled it. Assured that it was secure he began to climb it. Half-aghast at Sherlock's agility and half-stunned by his boldness, John stepped back open mouthed.

"Sherlock! What are you doing?"

"No way in from down there, some of these old building have skylights I might be able to look through".

He reached the roof and stood on top hands on hips looking proudly down. John muttered something about having the patience of a saint and too began to shimmy up the drainpipe. It took him considerably longer than Sherlock and when he finally reached the roof Sherlock had to hold out a hand to pull him up. John brushed himself down and they both turned around to survey the roof. No skylights. Sherlock groaned and took a few steps forward, John followed, quietly assessing whether they would be getting off the roof the same way they got onto it. Suddenly there was a groaning and creaking and the roof gave way beneath their feet.

John was falling before he had time to shout.

His landing was somewhat softer than he had anticipated. He had landed on a mattress, from what he could feel. A split second later Sherlock landed on top of him along with small pieces of broken tile and rubble, his arm hitting John on the stomach. John yelped and Sherlock leaped up.

"So I guess the great detective forgot that old roofs are not all that stable! Lucky this mattress was here or we would both have broken our necks, clearly someone is looking out for us today."

He massaged his stomach from where Sherlock's bony arm had collided with it. Sherlock didn't reply and had taken small torch out of his pocket and was surveying the huge expanse they had landed in. John looked down as Sherlock swept the light from the torch over the mattress.

It was covered in dried blood. John jumped from the mattress and began to breathe rapidly.

"Sherlock..." John trailed off as they both heard a noise in the dark; John estimated that it was about 10m away. The noise grew louder and John –straining his ears- heard a shuffling noise. Sherlock pointed the torch at the noise and let out a gasp of horror. A human figure was making their way towards them, its ragged clothes were covered in blood its head was tilted and it was –_groaning_. It was ashen faced, open mouthed and reaching out to both of them. John and Sherlock were running before they could see anymore.


	4. Chapter 4

John opened his eyes again and the living room materialised around him. He looked down and Sherlock was still on the floor. John lifted up his own shirt and saw a purple bruise where Sherlock's arm had collided with him when they both fell through the roof.

"We have to go and tell Lestrade" John said quietly.

"No we don't" replied Sherlock.

"We can't just let that thing roam the streets. You broke a door down remember, it could escape!"

Sherlock sighed and sat up without using his arms.

"Sherlock, you just don't want to go and see Lestrade because you're afraid _Daddy_ will tell you off for disobeying him".

Sherlock screwed up his face.

"Don't call him that. I just think it would be best if he didn't know."

"Well, I'm going! You can either come with me or stay down there on the floor."

John walked dramatically into the hallway and started putting on his coat, he went into his bedroom and retrieved his shoes, making enough noise so that Sherlock knew he was serious. Eventually Sherlock walked out of the living room and put his coat and scarf on without saying anything. Exchanging glances, they walked out of the flat.

Finishing recounting what had happened; John looked up at Greg Lestrade's face, who was sat behind his desk open mouthed.

"Have you two been smoking something? Is this some kind of joke?!"

John shook his head slowly.

"There has to be some kind of rational explanation" Greg said in response.

"I did try and tell him that" Said Sherlock through gritted teeth.

Greg made a noise of discontent and put his head in his hands. He sighed deeply.

"Well, I guess I will have to go down there, you two will have to come too, I cannot believe you went in there Sherlock! Actually yes I can! You've put my job on the line, not to mention this country's national security-"

"I hardly think the ambassador will start a war because someone went into his building!" Sherlock said laughing "and anyway we didn't go in through choice, gravity made the choice for us."

He was soon silenced when Greg flashed him a 'look that could kill'. He began to make calls. Sherlock recommended they take some large powerful lights to fully investigate, Lestrade gritted his teeth and nodded. John sensed that sometimes Lestrade did not always find Sherlock's 'help' all that helpful. Sherlock began to give directions to the alley that John and he had burst into after exiting the building and Lestrade repeated them to the officer on the other end of the phone.

They arrived at the alley along with 10 police offers, a few with police dogs and a forensic team, armed with forensic equipment and lighting equipment. The officers with the dogs rounded the corner into the alley first; one called out and Lestrade, Sherlock, John and a few other officers ran around the corner. There on the floor, by the broken door lay a figure. John ran up to it and knelt beside it.

"That's it that's the zombie!" he shouted.

It –rather he- was ashen grey, covered in blood and as John looked further also covered in huge bite marks. In daylight, it didn't look much like a zombie at all. John felt confusion burning inside him. He felt for a pulse but there was none. Lestrade radioed for an ambulance and the police officers with the dog entered the disused building. John and Sherlock quickly followed.


	5. Chapter 5

"So he was drugged?" John probed.

"Yes" Lestrade replied.

Sherlock was nowhere to be seen, no doubt hiding from the fact that he had indeed been wrong about the "zombie" in the warehouse.

"And the blood?"

"Tripped and fell on some broken glass and in his drugged stupor had smeared it everywhere. I guess that's what snagged all his clothes too." Lestrade added.

"So if Sherlock and I hadn't gone in there then he probably would have died?"

Lestrade exhaled slowly.

"Probably yes. The drugs were slowing his heart progressively and the blood loss hadn't helped.

"I guess that's why the ambassador didn't want the police going in there in the first place then."

"Yes. Although can I just say I am still _quite_ angry that you and Sherlock disobeyed me. It may have paid off this time but next time I ask you to back off I am saying it for a reason. Either to protect you or the reputation of this police force." Lestrade said firmly "and my job" he added quietly under his breath.

"He's been arrested then, the ambassador?"

"Yes. He is having a lovely chat with Sergeant Donovan now."

John snorted at the prospect and said goodbye to Greg. He left the police station to find Sherlock hovering outside studying a windowsill. A few passersby looked on bemused but John didn't question his odd behaviour which for Sherlock- was perfectly normal behaviour.

"The whole "zombie" thing then. You were wrong" John said gleefully.

"Whoa! I never said it was a zombie. You did."

"But _you didn't actually _know what it was, did you?"

Sherlock looked sheepishly around.

"No. But we know now and look we saved a life!"

"We did indeed. Although, Greg's still pretty mad about the whole hacking his computer and going into the building shenanigans"

"Gregory Lestrade needs to get over his petulant behaviour. I cracked the case for him and saved a life."

John was impressed Sherlock had stored Lestrade's first name in his memory finally. He obviously considered it important information now.

"All this talk of the undead has made me hungry. Can we get some lunch?" John grumbled.

Sherlock looked at him and smiled.

"I might just push the boat out and have some toast"

"Blimey. Sherlock Holmes eating food!" John retorted. "Are you sure you haven't been drugged too?!"


End file.
